BITE-SIZE THEOLOGY (173): What do we mean by “Natural Law”?

Rev José Mario O Mandía


We read in the Book of Genesis that God created the universe through his Λόγος (Logos), his Word (“And God said…” – Genesis 1:3). St John adds, “All things were made through him [the Λόγος], and without him was not anything made that was made” (John 1:3).

Λόγος does not only mean “word.” Its many meanings include “reason,” “plan,” “principle” or “standard.” In other words, the universe was created with a plan in the mind of the Maker. That plan is called the “Eternal Law.”

What is the Eternal Law? St Thomas Aquinas, in his Summa Theologiae (I-II q93 a1) explains Eternal Law with an analogy. He says that every artist has, in his mind, the type and design of the thing he would like to fashion. The idea in the mind of the artist is the exemplar and model of what he would like to create. This exemplar acts as a kind of law that determines how the artist executes his work. So Divine Wisdom, too, has in His mind, the type and design, the plan, for His own creation. This design in His mind is the model, which we call the Eternal Law.


Let us extend the analogy cited above. Suppose now that the maker has finalized the design of the product he wants to make. He then starts to work on it, following the model in his mind (which he may have set down on paper), so that the mental model becomes a material reality. Ideally, the structure of the manufactured artifact should correspond to the model. That structure determines how the product works and functions.

So just in the same way the structure of the product corresponds to the model in the maker’s mind, the nature of man corresponds to the model in God’s mind. This nature determines how man works and functions. The mental model is the law in the maker’s mind; the nature of the final product is the law in the finished artifact. The model in God’s mind is the Eternal Law; man’s nature determines the law for man. This is one reason it is called “Natural Law.”

Peter Kreeft explains in his book Catholic Christianity (San Francisco: Ignatius Press, 2001, p 168): “Moral laws are based on human nature. That is, what we ought to do is based on what we are. ‘Thou shalt not kill,’ for instance, is based on the real value of human life and the need to preserve it. ‘Thou shalt not commit adultery’ is based on the real value of marriage and family, the value of mutual self-giving love, and children’s need for trust and stability.”

However, unlike the artifact that the artist is shaping, the object of God’s Eternal Law is a creature who can think and will, like its Maker. This creature, unlike the non-living work of the artist, has the option of accepting or rejecting the Master’s plan. Yes, that is the “terrible” power of our freedom: we can say yes, and we can say no to our all-good Father.

Another reason why it is called “Natural Law” is that it can be known by the natural light of reason (without the aid of faith). St Paul says that even the Gentiles have this law “written on their hearts” (Romans 2:15). The Maker, who is Lawmaker at the same time, presents this law to creatures who can understand it with their minds and interiorize it, or make it their own. He expects them to use their intellect and will – their freedom – to respond to it. God respects human nature to such an extent that He will never bypass our freedom. Peter Kreeft explains (Catholic Christianity, p 168): “The natural law is also naturally known, by natural human reason and experience. We do not need religious faith or supernatural divine revelation to know that we are morally obligated to choose good and avoid evil or to know what “good” and “evil” mean. Every culture in history has had some version of the Ten Commandments. No culture in history has thought that love, kindness, justice, honesty, courage, wisdom, or self-control was evil, or that hate, cruelty, injustice, dishonesty, cowardice, folly, or uncontrolled addiction was good.”

Nonetheless, the knowledge of this law varies from person to person. The CCCC (No. 417) explains: “Because of sin the natural law is not always perceived nor is it recognized by everyone with equal clarity and immediacy.”

This is why God spelt it out for us in “Divine Positive Law,” and why we need to educate our conscience. We will explain these in later essays.

Since the Natural Moral Law springs from man’s nature, we can understand why it is universal and immutable.

(1) Universal: every individual with a human nature is covered by it (cf. CCCC, No. 416).

(2) Immutable: man’s nature is the same today as when it was in the times of Adam and Eve. (Some people might, in fact, argue that the men of today are different from the men of yesterday. However, they are only speaking of non-essential changes, accidental changes) (cf. CCCC No.416).

(Photo: SHAWSHANK66 at Pixabay)